Cheap and easy internet filter..
I have been recently playing around with OpenDNS... A pretty slick and easy way to limit the websites that the computers on your network are able to visit...
My kids really like to play on the computer.. Mostly they play flash games online that Mom says are okay.. They play with Webkinz and beanie baby websites, PBS kids and the like.. They don't seem to get into much trouble, but on the internet trouble is often just a mistyped URL away... Typing is not the kid's strong suit yet.
Open DNS is handy. I just go into my router and insert Open DNS's address as the DNS server.. From then on any machines getting their network assignments from that router will send their requests through openDNS. Once you setup an account and give OpenDNS instructions on what kind of domains you want to allow or deny, you are done.
I set mine on the Low Setting... This blogs Porn and Phishing, but not the British Tabloids. You can crank it all the way up to the point where it blocks social networkings sites and the like.
It isn't foolproof, but it is far better than nothing.. Sites like Youtube.com are either on or off. It would be nice to have a some where in the middle setting..
Anyway, I don't think this is a replacement for adult supervision, but it does reduce the risk of ugly images passing before the children's eyes accidentally. I suspect it will also do a pretty nice job of preventing spyware from taking over your PC's. (Macs Rock)